The broad goal of this project is to advance our theoretical understanding of how early semantic development and language processing skills contribute to early infant risk for later language delays and impairments. We will examine infants with broad spectrum of language abilities, including those who are late-talking. Late talking infants are a group of children between 18-24 months of age who fall below the 20th percentile in early language measures. While many late talking children do catch up with their peers and show typical language growth, a subset will remain delayed and receive a diagnosis of specific language impairment (SLI). SLI is a language disorder that affects nearly 8% of school-aged children and results in difficulties in a range of language skills, and can lead to negative academic and social consequences. Children with SLI are not often identified until they are school-aged, although parents often report concerns about language growth that start from infancy. There is an urgent need not only to develop of measures that can identify which children are at greatest risk for language impairments in infancy and toddlerhood, but also to understand the mechanisms that underlie these language delays. Such advancements, in tandem, have the potential to yield crucial insights into how early intervention for early language delays may yield improved outcomes for these children. By investigating two promising markers of later language delay (1) early fluency and accuracy in lexical recognition, and (2) early semantic structure of vocabulary development, this project is can further refine measures that have shown early promise in identifying markers of language delay, and identify whether or not these skills are casually related. We assess whether a relationship exists between these factors, and if in combination they may improve identification of children who will remain delayed in language skills at age 3. The specific objectives of this proposal are to (1) evaluate the relationship between semantic domain knowledge and real-time recognition of words from 18-30 months, (2) explore whether and how word learning, semantic development, and processing skills are related and (3) assess whether language outcomes at 36 months relate to earlier measures acquired between 18-30 months. This project will highlight the importance of the ability to efficiently recognize, interpret and learn relationships between word meanings as a marker of later language delay, and will provide insights into the value of teaching semantic relationships between words as a potential approach for early intervention.